User:Abyssal/Portal:Ichthyosauromorpha
The Ichthyosauromorpha PortalIntroductionThe Ichthyosauromorpha are an extinct clade of marine reptiles consisting of the Ichthyosauriformes and the Hupehsuchia, living during the Mesozoic. The neural arch being reduced or absent.
The Ichthyosauromorpha were previously thought to have likely originated in China during the upper Lower Triassic period, about 248 million years ago. However, a 2023 study recorded the fossils of a derived marine ichthyosauromorph (an ichthyopterygian) in earliest Triassic rocks of Spitsbergen, Norway, just 2 million years after the Permian–Triassic extinction event. The presence of such a derived ichthyosauromorph so early in the Triassic indicates that the ichthyosauromorphs (and possibly ichthyosauriformes, depending on divergence estimates) originated during the Permian and were thus survivors of the mass extinction as opposed to ecological successors that evolved following it.
One branch consists of the Hupehsuchia, and the other of the Ichthyosauriformes, of which Cartorhynchus was a basal member. Other ichthyosauriforms were the Ichthyopterygia, containing the Ichthyosauria and allies. The last ichthyosaurs probably became extinct in the middle Cretaceous. Their relationships with other reptiles are unresolved, due to their highly derived morphology and presumed ancient origins, even in their earliest known representatives, though they are usually considered to be diapsids. A 2022 study on the early evolution of reptiles classified the Ichthyosauromorpha as basal archosauromorphs, forming a clade with the other marine reptile groups Thalattosauria and Sauropterygia as sister to the rest of the Archosauromorpha. A 2023 study describing the Triassic marine reptile Prosaurosphargis found a similar placement, albeit instead placing the three marine reptile groups within an expanded Archelosauria. (Full article... )
 The models represent fifteen ichthyosaurs and plesiosaurs from the Mesozoic era, as well as some mammals from the more recent Cenozoic era. (see more... )
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